1. Field of the Invention
The present invention relates to couplers for joining the ends of successive lengths of pipe, conduit or other related components, and in particular to couplers for joining the ends of successive pipes or other components (e.g., an exhaust manifold) in an exhaust system for vehicles.
2. The Prior Art
It is well known that, in vehicle exhaust systems, particularly those for heavy duty vehicles, such as large trucks, the motors produce a significant amount of vibration in the exhaust system components. Operation of the motors at continuous speeds for prolonged periods of time can, especially, produce what are known as harmonic vibrations which can cause deflections of significant magnitude and/or frequency along the extended length of an exhaust system, from the exhaust manifold through to the tailpipe, unless otherwise attenuated. Repeated deflections of the exhaust system components can, in turn, cause one or more of the components to weaken with time and ultimately fail. Further, such harmonic vibrations will also be transmitted through the exhaust system components to the mountings of the components, promoting the loosening of the mountings, which can result in the sudden displacement of one or more components of the exhaust system, with the potential for both personal injury and equipment damage.
In addition to the vibrations created by the motor of the vehicle, an exhaust system is also subjected to various tension, compression and bending forces which arise during the operation of the vehicle. While individual components might be made stronger and more massive to resist failure by fatigue, such construction would be undesirable due to weight considerations. Further, by making individual elements stiffer, the vibrations are merely transmitted to the exhaust system mountings or other components, not reduced or eliminated. Accordingly, it is desirable to isolate the exhaust system, or at least components of the system from such vibrations and forces.
It is known that if the pipes of an exhaust system are divided and separated by non-rigid connections, rather than as continuous extended lengths, the development of harmonic vibrations from the motor is precluded or reduced. Such non-rigid connections can be advantageously employed to absorb other tension, compression and bending forces, in addition to motor vibrations.
It is therefore desirable to provide a coupler for joining successive components of an exhaust system, which coupler joins the successive components in a non-rigid fashion and is capable of absorbing tension, compression and bending forces, without transmitting them from one component to the next.
An example of a prior art coupler is U.S. Pat. No. 4,792,161 to Usui. In Usui, a pair of concentrically arranged, non-sealing spring coils are utilized to provide a mechanical connection between the pipes to be joined. One drawback of the coupler in Usui is that when the coils are in a stretched or bent position, gaps may form between individual bights of the coil, into which dirt, debris and moisture may invade, which may interfere with the operation of the coils, and lead to ultimate degradation of the coils through abrasion, rusting, and so forth. In addition, the coils (which are arranged one threaded within the other) are unprotected and exposed to the elements at all times, and are thus susceptible to damage from abrasion and other harmful physical contact. A further drawback of the coupler in Usui is that a sealing ring, positioned between overlapping pipe ends, is relied upon to provide sealing means to prevent escape of the exhaust gases. The sealing ring is subjected to cyclical flexure, tension and compression forces which will can ultimately compromise the seal to potentially require replacement of the coupler.
Another example of a vibration decoupling flexible connector is Udell, U.S. Pat. No. 5,145,215. In the apparatus of Udell, two liner tubes are provided which have overlapping free ends. The inner one of the overlapping tubes has a radially outwardly extending flange emanating from the tip of its free end. The outer one of the overlapping tubes has a radially inwardly extending flange emanating from the tip of its free end. The two flanges define an axially bounded annular space, in which is positioned a cylindrical annular spacer member. In one embodiment of the Udell apparatus, the annular spacer member is fabricated as a compressed metal mesh ring, which is porous, to at least some degree. A bellows member circumferentially surrounds and axially overlaps the overlapping region of the inner and outer liner tubes. The bellows is affixed, directly or indirectly, to the liner tubes. The axially outer ends of the liner tubes are then affixed to upstream and downstream exhaust system components, such as a downpipe from an exhaust manifold (upstream) and a length of exhaust tube (downstream).
Because the inner and outer liner tubes and the annular spacer member are all circular in cross-section, there is less resistance in the overlapping liner tubes and spacer member, to torsional forces (e.g., twisting of one or the other of the components around the common longitudinal axis of the joint). Typically, the downstream exhaust tube is clamped against such torsionally prompted twisting. Therefore, if the upstream exhaust component (e.g., the exhaust manifold) undergoes twisting movements, this twisting torsional force could be transferred to the upstream liner tube and, in turn, to the upstream end of the bellows. Because the downstream end of the bellows is affixed to the downstream liner tube, and, in turn, to the downstream exhaust system component, the bellows itself takes the brunt of the torsional shearing load. Bellows, typically, are not well suited to prolonged or repeated exposure to significant torsional loads, which loads could have adverse effects on the performance and durability of such bellows--relative to bellows structures which are not exposed to such torsional loads.
It is therefore an object of this invention to provide a flexible coupler for placement between successive components in an exhaust system for damping and blocking the transmission of vibration and other forces from one component to the next which is durable and not subject to attack by dirt, debris and the elements.
Yet another object of the invention is to provide a flexible coupler which does not utilize a sealing means positioned between moving exhaust system components which may cause the seal to prematurely yield requiring replacement of the coupler.
It is further an object of this invention to provide a flexible coupler for exhaust system components which provides means for mechanically connecting the ends of the components to be joined, which means are themselves protected from interference and/or degradation by external forces and elements.
Still yet another object of the invention is to provide a flexible coupler apparatus for exhaust system components which provides improved audio isolation to reduce or preclude migration of motor noise into the passenger compartment of the vehicle.
A still further object of the invention is to provide a flexible coupler for exhaust system components which incorporates a bellows member for preventing leakage of exhaust gases, which further provides means for protecting the bellows structure from torsional loads to which it may be exposed.
These and other objects of the invention will become apparent in light of the present specification, claims and drawings.